| # Browser View Resizer |
| |
| To fix bug [458](http://code.google.com/p/chromium/issues/detail?id=458), which |
| identifies that it is hard to hit the thin window frame corner to resize the |
| window. It would be better to have a resize hit area (called widget from now on) |
| in the corner, as we currently have for edit boxes for example. |
| |
| [TOC] |
| |
| ## Background |
| |
| This is specific to the Windows OS. On the Mac, Cocoa automatically adds a |
| resize widget (Not sure about Linux, we should double check). On Windows, those |
| resize widgets are at the extreme right of a status bar. For example, if you |
| remove the status bar from a Windows Explorer window, you lose the resize |
| widget. But since Chrome never ever has a status bar and simply take over the |
| bottom of the window for specific tasks (like the download shelf for example), |
| we need to find a creative way of giving access to a resize widget. |
| |
| The bottom corners where we would like to add the resize widget are currently |
| controlled by the browser view, which can have either the tab contents view or |
| other dynamic views (like the download shelf view) displayed in this area. |
| |
| ## Requirements |
| |
| Since there is no status bar to simply fix a resize widget to, we must |
| dynamically create a widget that can be laid either on the tab contents view or |
| on other views that might temporarily take over the bottom part of the browser |
| view. |
| |
| When no dynamic view is taking over the bottom of the browser view, the resize |
| widget can sit in the bottom right corner of the tab contents view, over the tab |
| contents view. |
| |
|  |
| |
| The resize widget must have the same width and height as |
| the scroll bars so that it can fit in the corner currently left empty when both |
| scroll bars are visible. If only one scroll bar is visible (either the |
| horizontal or the vertical one), that scroll bar must still leave room for the |
| resize widget to fit there (as it currently leave room for the empty corner when |
| both scroll bars are visible), yet, only when the resize widget is laid on top |
| of the tab contents view, not when a dynamic shelf is added at the bottom of the |
| browser view. |
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| If another view (e.g., again, the download shelf) is added at the bottom of the |
| browser view, below the tab contents view, and covers the bottom corners, then |
| the resize widget must be laid on top of this other child view. Of course, all |
| child views that can potentially be added at the bottom of the browser view, |
| must be designed in a way that leaves enough room in the bottom corners for the |
| resize widget. |
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| Since the bottom corners might have different colors, based on the state and |
| content of the browser view, the resize widget must have a transparent |
| background. |
| |
| The resize widget is not animated itself. It might move with the animation of |
| the view it is laid on top of (e.g., when the download shelf is being animated |
| in), but we won't attempt to animate the resize widget itself (or fix it in the |
| bottom right corner of the browser view while the other views get animated it). |
| |
| ## Design |
| |
| Unfortunately, we must deal with the two different cases (with or without a |
| dynamic bottom view) in two different and distinct ways. |
| |
| ### Over a Dynamic View |
| |
| For the cases where there is a dynamic view at the bottom of the browser view, a |
| new view class (named `BrowserResizerView`) inheriting from |
| [views::View](https://src.chromium.org/svn/trunk/src/chrome/views/view.h) is used |
| to display the resize widget. It is set as a child of the dynamic view laid at |
| the bottom of the browser view. The Browser view takes care of properly setting |
| the bounds of the resize widget view, based on the language direction. |
| |
| Also, it is easier and more efficient to let the browser view handle the mouse |
| interactions to resize the browser. We can let Windows take care of properly |
| resizing the view by returning the HTBOTTOMLEFT or HTBOTTOMRIGHT flags from the |
| NCClientHitTest windows message handler when they occur over the resize widget. |
| The browser view also takes care of changing the mouse cursor to the appropriate |
| resizing arrows when the mouse hovers over the resize widget area. |
| |
| ### Without a Dynamic View |
| |
| To make sure that the scroll bars (handled by `WebKit`) are not drawn on top of |
| the resizer widget (or vice versa), we need to properly implement the callback |
| specifying the rectangle covered by the resizer. This callback is implemented |
| on the `RenderWidget` class that can delegate to a derive class via a new |
| virtual method which returns an empty rect on the base class. Via a series of |
| delegate interface calls, we eventually get back to the browser view which can |
| return the size and position of the resize widget, but only if it is laid out on |
| top of the tabs view, it returns an empty rect when there is a dynamic view. |
| |
| To handle the drawing of the resize widget over the render widget, we need to |
| add code to the Windows specific version of the render widget host view which |
| receives the bitmap rendered by WebKit so it can layer the transparent bitmap |
| used for the resize widget. That same render widget host view must also handle |
| the mouse interaction and use the same trick as the browser view to let Windows |
| take care of resizing the whole frame. It must also take care of changing the |
| mouse cursor to the appropriate resizing arrows when the mouse hovers over the |
| resize widget area. |
| |
| ## Implementation |
| |
| You can find the changes made to make this work in patch |
| [16488](https://codereview.chromium.org/16488). |
| |
| ## Alternatives Considered |
| |
| We could have tried to reuse the code that currently takes care of resizing the |
| edit boxes within WebKit, but this code is wired to the overflow style of HTML |
| element and would have been hard to rewire in an elegant way to be used in a |
| higher level object like the browser view. Unless we missed something. |
| |
| We might also decide to go with the easier solution of only showing the resize |
| corner within the tab contents view. In that case, it would still be recommended |
| that the resize widget would not appear when dynamic views are taking over the |
| bottom portion of the browser view, since it would look weird to have a resize |
| corner widget that is not in the real... corner... of the browser view ;-) |
| |
| We may decide that we don't want to see the resize widget bitmap hide some |
| pixels from the tab contents (or dynamic view) yet we would still have the |
| resizing functionality via the mouse interaction and also get visual feedback |
| with the mouse cursor changes while we hover over the resize widget area. |
| |
| We may do more research to find a way to solve this problem in a single place as |
| opposed to the current dual solution, but none was found so far. |
